Voyager Has Left The Building

The Voyager 1 probe is about to reach a pretty cool milestone in the annals of spaceflight and discovery

It will, kinda soon, officially exit the solar system!

Anyone remember september 5 1977? I have a vague memory of that day primarily because of the launch of Voyager 1.

The launch of this probe (and its twin) gave us an unprecedented look at the largest planets in the solar system–Jupiter and Saturn, Neptune and Uranus. I remember eagerly waiting for the latest images of these colossal gas giants that so dominant our solar system.

Astronomer Neils Tysone Degrassi recently made an interesting point regarding this. The Voyagers not only helped us appreciate and understand these behemoths but also how diverse and interesting their tiny moons can be…Europa, Io, Titan, Ganymede etc. In many ways these are more interesting than the planets themselves.

So that was the first part of Voyager’s career. How can there be anything left to do? Isn’t it just an insensate hulk blindly flying though space?

I don’t think it’s uncommon to believe that the solar system officially ends after the last planet, Neptune or maybe after the kuiper belt objects like ummmm what’s it called…..oh yeah pluto. It’s a bit subjective but astronomers consider the best definition to be the end of the influence of the sun in space (except of course for the photons).

To understand the neighborhood of our solar system you have to consider the following.

Heliosphere
This is essentially the irregularly-shaped bubble in space occupied by our solar system. The solar wind or charged particles emanating from the sun push away the interstellar medium around us, namely the hydrogen and helium gas permeating the galaxy.

Heliosheath
This is the outer envelope of the heliosphere. This can be as far away as 100 a.u. (astronomical unit = 93 million miles or the earth-sun separation) The solar wind has slowed down in this area and is turbulently mixing with normal interstellar space. The real milestone with Voyager now is that it will be leaving the heliosheath soon because the the solar wind has essentially stopped moving radially outwards and is pretty much going sideways

Heliopause
This is the last exit in our solar system. The solar wind is too weak to push back the winds from other stars. Once Voyager crosses this boundary in 2014, it will finally be exiting our solar system and entering the true interstellar medium

This whole topic is of course deliciously more complicated with other regions like the termination shock, bow shock, hydrogen wall. If I’ve piqued your interest at all please look this stuff up.